People generally spend a considerable amount of time sitting in a chair. Traditionally, chairs place the legs of the user in a substantially right-angled position, where the thigh is positioned substantially perpendicularly with the rest of the leg. Therefore, elevating oneself from a seated position into an upright or standing position typically requires the user to have a sufficient amount of knee flexibility, balance, and muscular strength in order to safely get in and out of the chair.
For most people, getting into and out of a chair is not a problem. For others, however, it is. For example, some people suffer from a variety of disorders and diseases that make transitioning from a seated position to a standing position (and vice versa) extremely difficult, and in some cases, impossible. Users having arthritic knee joints, for example, could have reduced mobility and flexion of the knees. Additionally, people with certain neurological disorders or diseases, such as Parkinson's disease, have great difficulty in maintaining their balance. Regardless of the particular malady, however, such difficulty in getting into and out of a chair can increase stress on the user's muscles and joints, increase fatigue, and increase risk of physical injury.